AlN Passivation Research Articles

High breakdown voltage in AlN/GaN metal–insulator–semiconductor high-electron-mobility transistors

The breakdown characteristics of AlGaN/GaN based metal–insulator–semiconductor high-electron-mobility transistors (MISHEMTs) using a 10 nm thick AlN gate insulator and passivation layer deposited plasma enhanced atomic layer deposition. The AlN was effective in significantly reducing gate leakage current relative to Schottky gate devices and showed only small decreases in drain current during gate lag measurements. The devices exhibited a strong dependence of gate breakdown voltage on source–drain distance, reaching a value of 2000 V for a source–drain distance of 40 μm limited by the measurement instrument. The specific on-state resistance was 1.3 and 10.9 mΩ cm2 for the devices with the gate–drain distance of 7.5 and 37.5 μm, respectively. The saturation drain current was inversely dependent on source–drain distance and the on–off ratios were in excess of 108 due to the low gate leakage current in the MISHEMTs.

Influence of AlN Passivation on Dynamic ON-Resistance and Electric Field Distribution in High-Voltage AlGaN/GaN-on-Si HEMTs

We investigate in detail the influence of AlN passivation on dynamic ON-resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> ) and electric field (E-field) distribution in high-voltage AlGaN/GaN high electron mobility transistors (HEMTs) on a Si substrate based on pulsed I-V measurements, electroluminescence (EL) microscopy, and 2-D physics-based numerical device simulations. It is found that the dynamic RON increase has been significantly suppressed to below 10% at various temperatures ranging from -50 to 200 °C owing to the effective and robust compensation of deep acceptor-like trap states at the AlN/GaN (passivation/cap) interface by the additional positive polarization charges induced in the epitaxial AlN thin passivation layer grown in a plasma-enhanced atomic layer deposition system. To the best of our knowledge, this is the first time that highly suppressed current collapse in an AlGaN/GaN HEMT on a Si substrate within a wide temperature range is ever reported. By monitoring the dynamic RON for 100 consecutive 133-kHz switching cycles, its variation is observed to be less than 2.5%, indicating excellent stability of the passivation effectiveness. The electric field in an AlN-passivated device is found to be well confined at the drain-side gate edge, as shown in EL measurement and numerical simulation results. This phenomenon directly suggests that the virtual gate effect arising from surface trap charging has been effectively alleviated by the AlN passivation technique.

Nitride passivation reduces interfacial traps in atomic-layer-deposited Al2O3/GaAs (001) metal-oxide-semiconductor capacitors using atmospheric metal-organic chemical vapor deposition

Using an atmospheric metal-organic chemical vapor deposition system, we passivated GaAs with AlN prior to atomic layer deposition of Al2O3. This AlN passivation incorporated nitrogen at the Al2O3/GaAs interface, improving the capacitance-voltage (C–V) characteristics of the resultant metal-oxide-semiconductor capacitors (MOSCAPs). The C–V curves of these devices showed a remarkable reduction in the frequency dispersion of the accumulation capacitance. Using the conductance method at various temperatures, we extracted the interfacial density of states (Dit). The Dit was reduced over the entire GaAs band gap. In particular, these devices exhibited Dit around the midgap of less than 4 × 1012 cm−2eV−1, showing that AlN passivation effectively reduced interfacial traps in the MOS structure.

High-$f_{{\rm MAX}}$ High Johnson's Figure-of-Merit 0.2- $\mu{\rm m}$ Gate AlGaN/GaN HEMTs on Silicon Substrate With ${\rm AlN}/{\rm SiN}_{{\rm x}}$ Passivation

This letter reports a 0.2- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\rm m}$</tex></formula> gate AlGaN/GaN high-electron-mobility transistors (HEMTs) on an Si substrate passivated with an <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm AlN}/{\rm SiN}_{{\rm x}}$</tex> </formula> (4/20 nm) stack layer. The 4-nm-thick AlN was grown by plasma-enhanced atomic-layer-deposition. The <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm AlN}/{\rm SiN}_{{\rm x}}$</tex></formula> -passivated HEMTs exhibit a high maximum drain current of 930 mA/mm, an three-terminal OFF-state breakdown voltage <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$({BV}_{{\rm DS}})$</tex></formula> of 119 V, and a small threshold voltage shift of 130 mV in a wide drain bias range <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(V_{{\rm DS}}=3-24~{\rm V})$</tex></formula> . Owing to the additional positive polarization charge in the AlN passivation layer, the access resistance <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$R_{s}$</tex> </formula> in the GaN-on-Si HEMTs is significantly reduced while maintaining small parasitic gate-drain capacitance <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$C_{{\rm gd}}$</tex></formula> , contributing to a high power-gain cutoff frequency <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$f_{{\rm MAX}}$</tex></formula> of 182 GHz and a high Johnson's figure of merit of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${BV}_{{\rm DS}}\times f_{\,T}$</tex></formula> of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$6.43\times 10^{{12}}~{\rm V}/{\rm s}$</tex></formula> simultaneously. The accuracy of the RF performance is verified by a small signal modeling based on measured S-parameters.

Effects of interface oxidation on the transport behavior of the two-dimensional-electron-gas in AlGaN/GaN heterostructures by plasma-enhanced-atomic-layer-deposited AlN passivation

The effects of interface oxidation on the transport behavior of the 2-D electron gas (2DEG) in AlGaN/GaN heterostructures by plasma-enhanced-atomic-layer-deposited AlN (PEALD-AlN) passivation were investigated using temperature-dependent Hall-effect and X-ray photoelectron spectroscopy (XPS) characterizations. AlGaN/GaN heterostructure with a 4-nm-thick PEALD-AlN passivation exhibits good 2DEG transport behavior and stability at moderately high temperature (e.g., 275 °C). However, serious oxidation of the AlN/GaN (cap layer) interface occurs as the sample is heated up to 400 °C in low-pressure atmosphere, as verified by an increased Ga-O bond in Ga 3d core-level spectra. The oxidation leads to a significant reduction of 2.47 × 1012 cm−2 in the 2DEG density in the channel. A modified AlN passivation structure with Al2O3/AlN (10/4 nm) stack is shown to be able to effectively suppress the oxidation of the AlN/GaN interface, demonstrating an enhanced 2DEG density and high-temperature stability even when the sample is heated up to 500 °C. Based on XPS and 2DEG recovery experiments, it is suggested that acceptor-like deep levels have been generated in the near-surface region of AlGaN/GaN heterostructure because of the oxidation, and trapping of these deep levels results in significant depletion of the 2DEG in the channel. The effects of PEALD-AlN passivation on the strain in the AlGaN barrier of AlGaN/GaN heterostructures are also evaluated with high-resolution X-ray diffraction technique.

Analysis of diamond surface channel field-effect transistors with AlN passivation layers

Diamond surface channel field effect transistors were passivated with thin AlN layers grown by metal-organic chemical vapor deposition in order to improve the chemical stability of the surface-near p-type channel. Electrical characterization showed that the surface-near conductivity in the diamond is preserved during AlN overgrowth if the process temperature does not exceed 800 °C. However, the sheet carrier density is decreased by a factor of about 5 compared to the unpassivated hydrogen-terminated surface. A combination of TEM and XPS analysis showed that this effect is not induced by a partial modification of the surface termination or by a polarization of the AlN passivation. The preserved, but reduced surface-near conductivity in the diamond can however be explained by a hydrogen double bond between the diamond and the AlN film. Field-effect transistor structures fabricated on the passivated diamond substrates showed stable operation up drain-source voltages to −70 V and might therefore be promising candidates for future high-voltage applications.

Atomic Layer Epitaxy AlN for Enhanced AlGaN/GaN HEMT Passivation

Enhancements in AlGaN/GaN high-electron-mobility transistor (HEMT) performance have been realized through ultrathin (4 nm) AlN passivation layers, formed by atomic layer epitaxy (ALE). A combination of ex situ and in situ surface cleans prepare the surface for deposition of ALE AlN. HEMTs passivated by high crystallinity AlN, grown at 500 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}{\rm C}$</tex></formula> , show improvements in 2-D electron gas sheet carrier density, gate leakage current, off-state drain leakage current, subthreshold slope, and breakdown voltage. In addition, degradation of dynamic on resistance during pulsed off-state voltage switching stress is suppressed by <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\sim}{50\%}$</tex></formula> compared with HEMTs passivated by conventional plasma enhanced chemical vapor deposition <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm SiN}_{x}$</tex></formula> .

Passivation of In0.53Ga0.47As/ZrO2 interfaces by AlN atomic layer deposition process

Reducing defects at III-V/high-k interfaces is essential for optimizing devices built on these materials. Here, the role of an interfacial AlN process at In0.53Ga0.47As/ZrO2 interfaces is investigated by hard x-ray photoelectron spectroscopy (HAXPES) and capacitance/voltage (C-V) measurements. C-V measurements show a significant reduction in the density of interface traps with the interfacial AlN process and a capping TiN layer. To elucidate the specific role of the AlN process, blanket films with various deposition processes are compared. The AlN process alone (without subsequent dielectric deposition) reduces InGaAs oxide levels below the HAXPES detection limit, even though the AlN is ultimately found to be oxidized into AlOx with only trace N incorporation, yet AlN passivation provides a lower Dit (density of interface traps) when compared with an H2O-based Al2O3 deposition. The AlN process does not passivate against re-oxidation of the InGaAs during an O3 based ZrO2 deposition process, but it does provide passivation against As-As development during subsequent TiN deposition. The role of chemical defects in the C-V characteristics is also discussed.

AlN passivation by plasma-enhanced atomic layer deposition for GaN-based power switches and power amplifiers

Developing an effective passivation technique for AlGaN/GaN high-electron-mobility transistors (HEMTs) is of primary importance to keep pace with the advancement of GaN-based high-voltage power switches and high-power amplifiers. In this work, effective passivation of AlGaN/GaN HEMT has been developed using a monocrystal-like AlN thin film grown by plasma-enhanced atomic layer deposition (ALD) (PEALD). Significant current collapse suppression and dynamic ON-resistance reduction are demonstrated in the PEALD-AlN-passivated AlGaN/GaN HEMTs, especially under high-drain-bias switching conditions. An output power density of 2.64 W mm−1 at 2 GHz is achieved on the PEALD-AlN-passivated GaN-on-Si HEMTs without the use of the field-plate. The physical mechanism of the PEALD-AlN passivation of AlGaN/GaN HEMTs is systematically investigated with high-frequency and quasi-static capacitance–voltage (C–V) characterizations, and a novel passivation scheme using polarization charges in passivation materials to compensate the slow-response interface trap states is proposed.

Mechanism of PEALD-Grown AlN Passivation for AlGaN/GaN HEMTs: Compensation of Interface Traps by Polarization Charges

The physical mechanism of passivation of AlGaN/GaN HEMTs by AlN thin film prepared with plasma-enhanced atomic layer deposition (PEALD) is investigated by characterizing <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Ni}{-} \hbox{Al}_{2}\hbox{O}_{3}/\hbox{AlN}{-}\hbox{GaN}/\hbox{AlGaN}/\hbox{GaN}$</tex></formula> metal–insulator–semiconductor (MIS) diodes. The dielectric stack <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \hbox{Al}_{2}\hbox{O}_{3}/\hbox{AlN}$</tex></formula> (13/2 nm) exhibits similar capability in suppressing the current collapse in AlGaN/GaN HEMTs as the 4-nm PEALD-AlN thin film used in our previous work but delivers much lower vertical leakage to facilitate the capacitance–voltage characterizations. Exceptionally large negative bias ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ &lt; -\hbox{8}\ \hbox{V}$</tex></formula> ) is required to deplete the 2-D electron gas in the MIS diode's <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$C$</tex></formula> – <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$V$</tex></formula> measurement. By virtue of quasi-static <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$C$</tex></formula> – <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$V$</tex></formula> characterization, it is revealed that positive fixed charges of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim\hbox{3.2} \times \hbox{10}^{13}\ \hbox{e}/\hbox{cm}^{2}$</tex></formula> are introduced by the PEALD-AlN. The positive fixed charges are suggested to be polarization charges in the monocrystal-like PEALD-AlN. They can effectively compensate the high-density slow-response acceptor-like interface traps, resulting in effective suppression of current collapse.

Comparison of ammonia plasma and AlN passivation by plasma-enhanced atomic layer deposition

Surface passivation of GaAs by ammonia plasma and AlN fabricated by plasma-enhanced atomic layer deposition are compared. It is shown that the deposition temperature can be reduced to 150 °C and effective passivation is still achieved. Samples passivated by AlN fabricated at 150 °C show four times higher photoluminescence intensity and longer time-resolved photoluminescence lifetime than ammonia plasma passivated samples. The passivation effect is shown to last for months. The dependence of charge carrier lifetime and integrated photoluminescence intensity on AlN layer thickness is studied using an exponential model to describe the tunneling probability from the near-surface quantum well to the GaAs surface.

High-k GaAs metal insulator semiconductor capacitors passivated by ex-situ plasma-enhanced atomic layer deposited AlN for Fermi-level unpinning

This paper examines the utilization of plasma-enhanced atomic layer deposition grown AlN in the fabrication of a high-k insulator layer on GaAs. It is shown that high-k GaAs MIS capacitors with an unpinned Fermi level can be fabricated utilizing a thin ex-situ deposited AlN passivation layer. The illumination and temperature induced changes in the inversion side capacitance, and the maximum band bending of 1.2 eV indicates that the MIS capacitor reaches inversion. Removal of surface oxide is not required in contrast to many common ex-situ approaches.

Initial reaction mechanism of H-passivated Ge surface passivation by atomic layer deposition of Al 2O 3 and AlN

The authors investigated the surface passivation mechanisms of H-terminated Ge(100)(2 × 1) by atomic layer deposition of Al 2O 3, AlN through first-principles calculation method. The formation of initial Al 2O 3 and AlN passivation layer on Ge surface is investigated at atomic scale and the corresponding reaction pathways for both the reaction are also presented. The reaction barrier heights of H 2O and NH 3 half reaction are 0.53 eV/mol and 0.51 eV/mol higher than that of Al(CH 3) 3 half reaction, respectively which indicates that the overall passivation processes of the both reactions are limited by the second half reaction. Moreover, the chemisorption state and product state of the NH 3 half reaction are found to be in the same energy level, and it is possible that the second half reaction of AlN will be trapped in a chemisorption state.

AlN Passivation Layer-Mediated Improvement in Tensile Failure of Flexible ZnO:Al Thin Films

AlN passivation layer-mediated improvement in tensile failure of ZnO:Al thin films on polyethersulfone substrates is investigated. ZnO:Al films without any passivation layer were brittle with a crack-initiating bending strain εc of only about 1.13% with a saturated crack density ρs of 0.10 μm(-1) and a fracture energy Γ of 49.6 J m(-2). On passivation by an AlN overlayer, the fracture energy of the system increased considerably and a corresponding improvement in εc was observed. AlN layers deposited at higher discharge powers yielded higher fracture energy and exhibited better performance in terms of εc and ρs.

RESIDUAL STRESS DEVELOPMENT IN CU THIN FILMS WITH AND WITHOUT AlN PASSIVATION BY CYCLIC PLANE BENDING

Since the thin film technology is applied to micro-machines, MEMS (micro electro-mechanical system), optical devices and others, the evaluation of mechanical properties in thin films becomes to be important. On the other hand, there are differences in mechanical properties between bulk materials and thin films, but studies in this field have not yet been made enough. The present paper reports on the evaluation of the mechanical properties of Cu thin films with and without AlN passivation layer. Specimens with different thickness of Cu film were subjected to cyclic plane bending fatigue test. Residual stresses developed in the Cu films were measured in a sequence of bending cycles using X-ray diffraction method in order to understand the effect of film thickness and passivation layer on mechanical properties of Cu thin films.

AlN Passivation Over AlGaN/GaN HFETs for Surface Heat Spreading

Reduction of thermal resistance in AlGaN/GaN heterojunction field-effect transistors (HFETs) is critical for further increase in their output power to be handled in these promising material systems. In this paper, we present a new technique to reduce it using polycrystalline AlN passivation deposited by dc sputtering as a surface heat spreader over AlGaN/GaN HFETs. The AlN is deposited by dc sputtering, and it is well oriented to the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</i> -axis. The measured thermal resistances of AlGaN/GaN HFETs with AlN passivation are lower than those with SiN passivation, which well agree with the results of the thermal simulation. The most notable change of the characteristics by AlN passivation is that the drain current increases by 30%, and the on-state resistance is reduced by 66% by the passivation; moreover, the current collapse suppresses successfully. As a result, the radio frequency output power is higher than that with conventional SiN passivation and is increased by increasing the thickness of AlN passivation. Thus, reduction of the thermal resistance and higher output power by AlN passivation is experimentally achieved.

X-Ray Investigation on Strength of Thin Films

The behavior of thermal stresses and residual stresses in aluminum and copper thin films were investigated by the diffraction of X-rays and synchrotron radiations. Aluminum films were exposed in an elevated temperature in order to measure the thermal stress behavior in the films. Thermal stresses in the films in thin aluminum and copper films of 10 nm to 1000 nm thickness with and without passivation payer were measured in a sequence of thermal cycles. Stresses in thick films without passivation traced along with a hysteresis loop during thermal cycles, whereas the thin films of nano-meter size with AlN passivation layer behaved in a linear way with the temperature change. Thin copper films with and without AlN passivation layer were used to investigate strengthening mechanism of thin films. Specimens with different thickness of the films were subjected to a cyclic plane bending fatigue test. Residual stresses developed in the films were measured in a sequence of bending cycles to understand the effect of film thickness and passivation layer on mechanical properties of thin films. The film of 500 nm thickness developed less residual stresses in the film than thicker films. A passivation layer was effective to prevent residual stress development in the film.

Recent advances in GaN transistors for future emerging applications

AbstractIn this paper, recent advances in GaN‐based transistors for power switching and millimeter wave communications are reviewed. These two applications are emerging in addition to the widely developed power amplifiers at microwave frequencies mainly for cellular base stations. Reduction of the fabrication cost is strongly required for power switching GaN transistors, which is enabled by our epitaxial growth technology on large area Si substrates. Another requisite for the application is to achieve normally‐off operation and our novel device structure called Gate Injection Transistors (GIT) enables it with low enough specific on‐resistance (Ron · A) and high drain current. Here, we also present the world highest breakdown voltage of 10400 V in AlGaN/GaN HFETs, extracting full advantage of the high breakdown strength of GaN. The used poly AlN passivation works as a surface heat spreader with its high thermal conductivity, which effectively relieves the channel temperature resulting in lower thermal resistances. The GaN device for future millimeter wave communication consists of MIS‐type gate using so‐called “in‐situ” deposited SiN as a gate insulator, which exhibits high fmax of 203 GHz and low noise figure of 1.4 dB at 28 GHz. The presented GaN transistors are promising for the two future emerging applications demonstrating high enough potential of the material systems. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Delay Time Analysis of AlGaN/GaN Heterojunction Field-Effect Transistors with AlN or SiN Surface Passivation

We have carried out delay time analysis for the high-frequency characteristics of AlGaN/GaN heterojunction field-effect transistors (HFETs) on sapphire substrates, focusing on a comparison between the effects of AlN and SiN surface passivation. HFETs with AlN passivation, in comparison with those with SiN passivation, exhibit high current gain cut-off frequencies fT with good flatness, in accordance with high intrinsic transconductance due to the self-heating reduction effect of AlN. From the delay time analysis, we find that the effective saturation electron velocity for AlN and SiN passivation is similar, while the electron mobility under the gate for AlN passivation is higher. This implies that the higher fT is mainly due to the higher electron mobility under the gate owing to the self-heating reduction by AlN passivation. This is consistent with the fact that the saturation velocity has a weak temperature dependence, while the mobility has a strong dependence.

Enhancement mode GaAs metal-oxide-semiconductor field-effect-transistor integrated with thin AlN surface passivation layer and silicon/phosphorus coimplanted source/drain

By using thin AlN film as a passivation layer between the GaAs and HfO2, GaAs metal-oxide-semiconductor (MOS) devices exhibited well-behaved accumulation and inversion capacitance-voltage characteristics with low leakage current of 6×10−5A∕cm2 at Vg=1V and interface state density of ∼4.9×1010cm−2eV−1. In order to improve the N+ source/drain activation efficiency, the Si∕P coimplantation technique was adapted to fabricate GaAs n-type metal-oxide-semiconductor field-effect-transistor (MOSFET). High quality N+∕P GaAs junction was achieved with extremely low junction leakage current of 3×10−6A∕cm2 at reverse bias of 1V and high forward current to reverse current ratio of Iforward∕Ireverse∼107 at GaAs source/drain junction. GaAs n-MOSFETs integrated with HfO2 gate dielectric and TaN gate electrode were fabricated by using AlN passivation layer and Si∕P coimplantation techniques. The results show that our GaAs n-MOSFETs operate in enhancement mode with Ion∕Ioff ratio of approximately six orders and good transfer and output characteristics.